BEIJING — Internet users in China were unable to access search giant Google Inc.’s main Web site or its Chinese service, and the company said Thursday it was investigating. The outage came after the China Internet Illegal Information Reporting Center last week accused Google of providing links to vulgar and obscene sites. Google, based in Mountainview, California, said it would do more to stop users in China from accessing pornography.

The outage began late Wednesday and affected Google’s main site, its Gmail.com e-mail service and its China-based site, Google.cn. On Thursday, all three were accessible from a computer in Beijing, but users in two other cities said they could not open Google’s main site or Gmail.

“We are investigating the matter and hope the service will be restored soon,” Google spokesman John Pinette in Hong Kong told The Associated Press.

The Chinese agency that oversees the Internet, the Ministry of Industry and Information Technology, did not immediately respond to requests for comment.

China has the world’s largest population of Internet users at more than 298 million. The communist government has the world’s most extensive Web monitoring and filtering system, and it regularly blocks access to foreign Web sites.

While the government claims the main targets are pornography, online gambling, and other sites deemed harmful to society, critics say that often acts as cover for detecting and blocking sensitive political content.

Authorities launched a crackdown this year that led to the closing of more than 1,900 porn-related Web sites.

Google has struggled to expand in China, where it says it has about 30 percent of the search market. The company launched Google.cn with a Chinese partner after seeing its market share erode as government filters slowed access to its U.S. service.

I have just checked the visitor stats for one of my blogs, Sudan Watch and can see there have been no visitors from China which is quite unusual. I'll keep an eye on the stats today to see if this blog post attracts a visitor from China. Usually they are quite on the ball.